358 PROF. ST. GEORGE MIYART ON THE 



the tenth, and is like it except that the prsezygapophyses again extend a little less 

 dorsad (as they have begun to do in the tenth vertebra), while from behind the summit 

 of each a sharp, pointed, metapophysial process extends dorsad, postaxiad, and externad. 

 The hyperapophyses are more developed (especially elongated) ; and there is uo longer 

 any trace of a neural spine. 



The median ventral ridge of the hsemal arch has here become a very sharp, plate-like, 

 prominent process. 



The TWELFTH VEETEBRA (Plate LVIII. fig. 33) is of about the same length as the 

 eleventh, and is like it except that the hind ventral process of the haemal arch is more 

 prominent, the hyperapophyses are larger, and the postzygapophyses here again begin 

 to fail to extend postaxiad so far as does the centrum. 



The THiRTEEXTn VERTEBRA is slightly shorter than the twelfth, and repeats its cha- 

 racters a little more strongly marked, except that the haemal arch projects preaxially 

 to the centrum in a somewhat less degree. The hyperapophyses project sharply and 

 strongly dorsad and preaxiad. 



The FOURTEEXTii VERTEBRA is again a little shorter. The postzj'gapophyses begin to 

 project postaxiad slightly beyond their articular surfaces. It has no longer the pointed 

 process just postaxial to the prsezygapophysis, or only a rudiment of such. Long cata- 

 pophysial ridges limit laterally the subcentral groove, though they altogether disappear 

 in the next vertebra. 



The FIFTEENTH VEETEBRA (Plate LVIII. figs. 34-36) is of about the same length as the 

 fourteenth. It is like it ; but the rib-like styloid processes are stouter, more externally 

 placed, and are more decidedly parapophysial. The hsemal canal has ceased to exist ; 

 and in its place is a long plate-like hypapophysis, which may be perforated. 



The hyperapophyses converge preaxiad, and may meet to indicate a rudiment of a 

 neural spine^. The postzygapophyses begin again to project postaxiad a little beyond 

 the centrum. 



The SIXTEENTH VERTEBRA is of about the same size as its serial predecessor, but differs 

 from it markedly in the sudden development of a long neural spine, curved postaxiad 

 at its tip. There is also a still larger plate-like hypapophysis, projecting postaxiad of 

 the centrum, and considerably larger than in the corresponding vertebra of Phala 

 crocorax. The prsezygapophyses begin again to extend preaxiad as much as does the 

 centrum. The rib-like styloid processes are shorter and stouter, and notched preaxially, 

 while the lamella, enclosing dorsally the lateral vertebral canal, extends more postaxiad, 

 and is therefore longer antero-posteriorly than in the fifteenth vertebra. 



The SEVENTEENTH VEETEBRA is of about the same size as the sixteenth ; but its neural 



' This vertebra, in the specimen of P. nov(B-hollandice in the Royal College of Surgeons' Museum, has a neural 

 spine more developed than has even the sixteenth vertebra of P. anhinga (in either specimen), while its four- 

 teenth vertebra is quite like the fourteenth vertebra of P. anhinga. This, coupled with the defective number 

 of cervical vertebrae, makes it probable that the fifteenth is lost in this specimen. 



